Bug Description

Semi-maximised windows show the same last button/indicator than normal windows: a square that is supposed to mean "click to maximise".
In fact, clicking that button in semi-maximised state brings the window back to its "restored" state.

This is confusing for the user.

This should be fixed by either:
- Keeping the button as it is but changing the effect to maximising the window; or
- Keeping the effect as it is, but changing the button so it resembles the one that a maximised window shows (a rectangle instead of a square)